Reflecting device



Jan. 24, 1933.

P. P. SANDFORD REFLECTING DEVICE Original Filed Dec. 3, 1924 PatentedJan. 24, 1933 UNITED STATES,

PATENT OFFICE PHILIP PUREFOY SANDFORD, 0F TEDDINGTON, ENGLAND,-ASSIGNOR, BY MESNE ASSIGNMENTS, TO JONATHAN C. STIMSON, OF ST. LOUIS,MISSOURI BEFLECTING' DEVICE Original application filed December 3, 1924,Serial No. 753,744, and in Great Britain December 3, 1923. Divided andthis application filed August 8, 1928. Serial No. 288,388.

This application is a division of my application for U. S. Patent filedDecember 3, 1924, No. 7 53,744.

This invention relates to reflecting devices, and more particularly todevices of the character having deflecting surfaces adapted to reflectlight impinging thereon at varying angles approximate the light source.The device is adapted for various purposes, such as a reflecting unitfor vehicles or for a letter, sign, or design suitable for use inadvertisements, display, decoration, etc. Where the device is used tomake up a letter, sign, or design, then the units are arranged along thestroke or strokes of the character.

Generally stated, in accordance with this invention, the reflectingdevice comprises a series of reflecting units arranged in contiguousrelation and having reflecting surfaces adapted to reflect lightimpinging thereon at varying angles back approximate the light source;the reflector, however, has a transparent, spheric front face overlyingand common to said units and through which the light passes. Inaccordance with one embodiment of this invention, the device is com-.posed of a transparent, prismatic plate having a series of totallyreflecting units on the back thereof, and this plate has a spheric frontface overlying and common to these n ts- In accordance with a particularembodiment described and illustrated, a number of tetrahedron may besuitably embodied in one reflector unit which 'is preferably mounted ina support or other mounting so as to exclude dust or moisture from itssurface. In one construction especially suitable for a rear reflector ona bicycle the unit may be mounted in a metal or other cup havingmeansfor attachment to the mudguard of the cycle. Preferably also the unit oreach glass element has a curved face so that the rays of light fallingupon the reflector will be reflected back with a small deviation to thedirection from which they strike the reflector, the deviation being suchthat they will be visible, for example, to the occupant of a vehicle ata distanoe of 100 yards.

The invention is illustrated in theaccomenclosure. f is a bolt on thecasing for securing it to a board or other suitable substance. Figure 4shows the unit a mounted in a recess g in a wood or other support h.

It will be understood that rays of light incident on the face of thelens will be reflected back substantially towards the source from whichthey emanated, so that the con vexity of the lens will cause a slightdivergence in a reflective beam. This effect may also be obtained byslight errors or roughnesses in moulding the glass or metal or othersurface.

It will be observed that at the back of the mounting or casing is an airspace indicated at i from which it is essential to exclude dust, sinceshould there be contact between the surface of the glass and themounting or case or if dust settles thereon, the refractive index wouldnot remain constant and consequently the effect obtained would bespoilt.

What I claim is':-

1. A sign forming element comprising a glass body having a slightlycurved front face and a plurality of right angled tetrahedra projectingfrom its rear face.

2. A sign forming element comprising a glass body having a slightlycurved front face and a plurality of right angled tetrahedra projectingfrom its rear face, and a support backing embracing the edges of thebody and enclosing the tetrahedra in spaced relation to form a dustexcluding air pocket.

3. A sign forming element comprising a circular glass disc having oneflat and one convex face, and a plurality of right angled tetrahedraprojecting from the flat face.

4. A reflecting device of the character described, comprising, a seriesof reflectin units arranged in contiguous relation and aving reflectingsurfaces adapted to reflect light impinging thereon at varying anglesback approximate the light source, the reflector having a transparentspheric front face overlying and common to said units and through whichthe light passes.

5. A reflecting device of the character described, comprising, atransparent rismatic plate having a series of totally re ecting units onthe back thereof, the reflecting,

surfaces of which are adapted to reflect light impinging thereon atvarying angles back approximate the light source, said plate having aspheric front face overlying and common to said units and through whichthe light passes.

' In testimony that I claim the foregoing as my invention I have signedmy name this 27th'day of July 1928. PHILIP PUREFOY SANDFORD.

